# Homework Help: A spaceship launched from a space station was moving with a speed 0.6c

1. Jan 9, 2012

### queenstudy

1. The problem statement, all variables and given/known data

A spaceship launched from a space station was moving with a speed 0.6c , with respect to the space station , in a direction perpendicular to its motion , when , a band of asteroids is observed a head of the ship. A proton gun is shut by the spaceship with a speed of 0.99c , in order to destroy it . what speed will an observer in the space station measure for these protons?

2. Relevant equations
using lorentz transformation of velocity but are there two components or only one ??

3. The attempt at a solution

2. Jan 9, 2012

### Dickfore

Re: relativity

$$\begin{array}{rcl} v_x & = & \frac{v'_x + V}{1 + \frac{v'_x \, V}{c^2}} \\ v_y & = & \frac{v'_y \, \sqrt{1 - \frac{V^2}{c^2}}}{1 + \frac{v'_x \, V}{c^2}} \end{array}$$

3. Jan 9, 2012

### queenstudy

Re: relativity

so there are 2 components?
can you give me the solution?

4. Jan 10, 2012

### tannerbk

Re: relativity

The way I read it, there is only one velocity component. As dickforce pointed out all you need to do is use the relativistic velocity transformation equation to find the speed of the protons from the point of view of an observer on the space station.

5. Jan 10, 2012

### queenstudy

Re: relativity

i know but do i use both components because according to the problem , its direction is perpendicular to its motion ?? so i guess we should find ux and uy

6. Jan 10, 2012

### queenstudy

Re: relativity

to me i saw it that there are two components

7. Jan 10, 2012

### vela

Staff Emeritus
Re: relativity

What is the speed of the space station? The problem statement implies it's moving, but you haven't said how fast it's going. You can't answer the question without knowing that.

8. Jan 10, 2012

### Staff: Mentor

Re: relativity

The wording seems a bit obscure, especially the part about 'in a direction perpendicular to its motion'. It's not clear what that statement refers to.

Let's say that the spaceship is launched along the x-axis of the space station. Are the protons fired in the x' direction or the y' direction, in the frame of the spaceship? (Solve it both ways.)

9. Jan 10, 2012

### queenstudy

Re: relativity

Doc AL , you are right the english language is weak , but let me tell you how i understood the question in the exam:
the photon gun is shooting in the y-axis while the ship is moving in the x-axis i dont know that's why i asked lol

10. Jan 10, 2012

### queenstudy

Re: relativity

Dc AL , thank you for your time
i know that is how it was written in the exam , word by word, my heart is telling me there is only one direction , but that sentence you pointed out is what made change my mind

11. Jan 10, 2012

### Staff: Mentor

Re: relativity

Are you sure that that is a word for word statement of the problem and not just your recollection?

In any case, if I had to guess what was meant I would guess as you did: The spaceship moves along the x-direction and the protons are fired along the y'-direction. That's the interpretation that makes the most sense and gives the most interesting problem.

12. Jan 10, 2012

### queenstudy

Re: relativity

so in this case we will need to find two components , i see thank you very much
and yes i wrote it as it is , the english language is weak i know